This invention relates to optical fiber testing, and more particularly to an optical fiber power, loss and polarity tester that incorporates a multi-fiber interface to enable efficient testing of cables and connections that have been terminated with multi-fiber connectors.
It is common practice to test loss and/or length of optical fiber after installation, repair, moves/adds/updates, etc. Today's most common topology consists of single-fiber connectors attached to single strands of fiber. These fibers are most often used in a duplex topology such that one fiber transmits network traffic in one direction and the other fiber transmits in the opposite direction. The individual fibers are often bundled into a large group within a cable but then individually terminated with a connector at each end of the fiber. FIG. 1 illustrates this common practice applied to a duplex fiber system wherein a main test unit 12 is connected to a fiber at a break-out and a remote test unit 14 is connected to the corresponding fiber at a remote end of the cable, and testing is performed by use of the two units.
Another common topology seen in today's high density data centers is to replace single fiber connectors with multi-fiber array connectors and cables as described in U.S. Pat. No. 6,004,042 and U.S. Pat. No. 6,931,193. It has been customary to terminate the multi-fiber array connectors into a break-out box (often called modules or cassettes). The break-out is accomplished through the use of a short set of fibers that are terminated to a multi-fiber array connector on one end and then to individual single fiber connectors at the opposite end. The boxes enable connection of the multi-fiber array cable plant to the duplex electronic equipment or cross-connects utilizing standard patch cords with single fiber connectors.
A new topology that is becoming more prevalent and has been standardized by IEEE in their 802.3ba-2010 standard for both 40 Gigabit Ethernet (40 GbE) and 100 Gigabit Ethernet (100 GbE) utilizes transceivers with multi-fiber array interfaces in the electronic equipment (instead of duplex interfaces) enabling patch cords with multi-fiber array connectors to be connected directly from the transceiver to the cable's multi-fiber termination. Therefore the need for the break-out boxes is eliminated. However, the elimination of the break-out box also eliminates the single fiber connector interface that is required for testing the cable plant. Prior art has continued to utilize the traditional test equipment with the single fiber interface by creating a break-out cable that is similar to the break-out box previously described, illustrated in FIG. 2. Some prior art is found in U.S. Pat. No. 5,940,559 and U.S. Pat. No. 5,196,899. This prior art makes testing of the cabling very slow and error prone. Additionally, a measurement of the polarity of the multi-fiber cable plant is highly desirable but prior art cannot do this automatically.
It is not obvious to those skilled in the art of optical fiber testing how to create an optical power, loss, and polarity tester for multi-fiber connectors. It is even less obvious how to do the same with the additional requirement of testing at multiple wavelengths. Testing at multiple wavelengths is common with duplex fiber testers, the main purpose of testing at multiple wavelengths being to ensure the cabling plant meets the loss budget at the wavelengths that will be running on the active network. It is also the purpose of testing at multiple wavelengths to utilize a long wavelength so to ensure no bending loss is present in the cabling plant. Optical fiber is typically more sensitive to bend losses at longer wavelengths.
It would be desirable to have a tester capable of easily testing multi-fiber connectors at single and multiple wavelengths.